Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 534743
Title Effects of current density, bicarbonate and humic acid on electrochemical induced calcium phosphate precipitation
Author(s) Lei, Yang; Saakes, Michel; Weijden, Renata D. van der; Buisman, Cees J.N.
Source Chemical Engineering Journal 342 (2018). - ISSN 1385-8947 - p. 350 - 356.
DOI http://dx.doi.org/10.1016/j.cej.2018.02.104
Department(s) Sub-department of Environmental Technology
WIMEK
Publication type Refereed Article in a scientific journal
Publication year 2018
Keyword(s) Bicarbonate - Electrochemical - Humic acid - Phosphate removal - Precipitation
Abstract Phosphorus (P) removal and recovery from sewage as calcium phosphate (CaP) by chemical precipitation is a widely used method. To avoid the addition of chemicals to increase the pH of the bulk solution and the need for a further separation step in conventional chemical precipitation process, we developed an electrochemical method, which can locally increase the pH near a Ti cathode. The separation of product and liquid then happens simultaneously by accumulating CaP at the electrode surface. The current density plays a crucial role in this system. A current density of 19 A/m2 results in the formation of crystalline CaP rather than amorphous CaP, but it does not enhance the removal of P in 24 h. Moreover, the current efficiency decreases with increasing current density. Furthermore, the increased H2 production at high current density may push the precipitated CaP back to the bulk solution, resulting in its dissolution. In the presence of bicarbonate (1–5 mM) or humic acid (1–20 mg/L), the removal of P was higher. This is probably due to the inhibited CaP precipitation in the bulk solution which in turn leaves more Ca and P ions available for the local precipitation on the cathode. However, bicarbonate at high concentration (10 mM) dropped P removal from 52 to 25%. This is caused by competition of carbonate and phosphate with the free Ca2+ ions and also by buffering the producted hydroxide ions at the cathode. The study shows that P can be removed as CaP by electrochemical precipitation at low current densities at common concentrations of bicarbonate and humic acid.
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